<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app">
    <input type="text" v-model="parentMessage">
    <my-component :message="parentMessage"></my-component>
</div>
<script src="https://unpkg.com/vue/dist/vue.min.js"></script>
<script>
    Vue.component('my-component',{
        props:['message'],
        template:'<div>{{ message }}</div>'
    });

    var app = new Vue({
        el:'#app',
        data:{
            parentMessage:''
        }
    })
</script>
</body>
</html>